Chop the walnuts and toast lightly in a dry non-stick pan until they release their aroma.
Wash the celery and cut into thin strips. Blanch briefly in boiling salted water.
Drain the celery, rinse under cold water and drain. Wash and core the apple, then cut into fine strips.
Mix the apple, celery, nuts and yogurt and season with salt, pepper, Worcestershire sauce and hot sauce.
Place some celery salad on each turkey slice, roll up and secure with cocktail sticks. Squeeze the lemon juice.
Halve the avocado, stone and peel. Cut the avocado flesh into slices and season with salt, pepper and 1-2 tbsp lemon juice. Drizzle with oil and place the turkey rolls on top.